SUN-091 Functional Links between ADP-Ribosylation and Phosphorylation on Histone H2B Regulate Adipocyte Differentiation

The differentiation of adipocyte precursors (preadipocytes) into mature adipocytes is a complex developmental process involving a carefully orchestrated transcriptional program, which is regulated by post-translational modification (PTM) of key target proteins. Our lab has recently demonstrated one such PTM, ADP-ribosylation, as a key regulator of adipogenesis through regulation of the transcriptional activity of the proadipogenic transcription factor, C/EBPβ. ADP-ribosylation is catalyzed by the PARP family of ADP-ribosyl transferases, which catalyze the transfer of ADP-ribose moiety from NAD(+) onto substrate proteins. Nuclear PARPs, such as PARP-1, are chromatin-binding proteins, which are associated with histone modifications and ongoing transcription. Thus, we hypothesized that histone ADP-ribosylation and its impact on other histone modifications could also regulate gene expression during adipogenesis. To test this possibility, we have used a variety of biochemical, molecular, cellular, genomic and proteomic analyses in 3T3-L1 cells. Using an NAD(+) analog-sensitive PARP (asPARP) approach coupled with mass spectrometry, we have identified specific sites of PARP-1-dependent ADP-ribosylation on histone proteins in preadipocytes. We found an interesting functional link between site-specific ADP-ribosylation and phosphorylation on histone H2B, which exerts its effects on the control of gene expression during the differentiation of adipocytes. Taken together, this study has elucidated a critical role for crosstalk between site-specific ADP-ribosylation and phosphorylation on histone H2B in modulating gene regulation that controls adipogenesis. This work is supported by a grant from the NIH/NIDDK (DK069710) to W.L.K.